Fiberglass is used to reinforce molded articles molded of plastic and elastomerics to enhance their mechanical strength and dimensional stability over thermal operating cycles.
The mechanical strength of a fiberglass reinforced plastic article has a direct relationship to the quantity of fiber glass contained within the moldable plastic. Also, the thickness of the glass fibers contributes to the mechanical strength of the article.
However, as the thickness of the glass fiber increases so does its prominence and visibility in the surface of the plastic molded article. A relatively coarse glass fiber impairs the smoothness and appearance of the surface of the article, and makes it unacceptable for product applications which require high surface quality, such as exterior body panels and trim components of automobiles unless additional processes or materials are used to finish the surface.
The prior art has addressed the problem of surface quality degradation by glass fiber reinforcement by techniques which are intended to mask the reinforcing fibers. These techniques increase the complexity and cost of manufacturing fiberglass reinforced plastic articles in high volume at commercial quality levels.
The service demands and operating environments of many plastic molded articles, such as automotive body panels and trim pieces, require mechanical strength and thermal stability which may be achieved by fiberglass reinforcement. The difficulty with the use of fiberglass in the molding of such articles has been its degradation of their surface quality.
The practical problem thus defined is the molding of a fiberglass reinforced plastic article Which enjoys the superior mechanical strength and thermal stability contributed by fiberglass without the impairment of surface quality. This problem is the subject of the published Japanese Patent Application titled "Glass Fiber-Reinforced Resin Composition," Application No. 60-21947, filed Feb. 8, 1985 by Hiromichi Uohashi and Tetsuji Kodaira, and published Aug. 16, 1986. That application discloses a glass reinforced plastic composition which employs glass fibers of diameter and length below preselected dimensional limits.
However, the patent does not address the problem of mixing the fibers with the plastic so that they become consistently spread throughout the plastic material. This problem is particularly acute with micro-fibers. The small, hair-like nature of such glass strands makes their intermixture with polymer resins difficult. Moreover, clusters of such fibers are not easily separated in a viscous polymer emulsion to provide a homogeneous dispersion of fibers in the polymer.